To say there is growing interest in mixed-use is like mentioning that lifestyle centers are mildly popular. Mixed-use projects are filling pipelines and portfolios from coast to coast and, as we examine the prolific format in this month’s real estate supplement “Mixed Use: Unmatched Success” (starting on page 119), I thought it would be helpful to pull together a definition of mixed-use that we could all agree on.

Not a chance.

No amount of research or polling gave me a lick of definition unanimity. But it did provide some interesting fodder for this column.

It appears clear that mixed-use’s beginnings are in land-use planning policies—as municipalities have pushed for developments that would provide housing, revitalize town centers and create more sustainable urban environments—but what mixed-use actually is is about as clear as mud. I found this little nugget in a 1998 study on mixed-use developments in England: “Whilst it is easy to define the unattractive, single-use, monocultural zone, it is less easy to define the attractive mixed-use zone.”

So mixed-use is pretty, while single-use isn’t.

The report did explore more than cosmetics, though. In discussing the redeveloped Brindleyplace project in Birmingham (England, not Alabama), researchers questioned whether or not the project is really mixed-use.

Why not? Brindleyplace has retail, office, residential, bars and restaurants, cultural facilities, a theater. What’s not mixed-use about it? “But,” the report argues, “few of the buildings accommodate layered uses with offices below and residential above.” Plus, the restaurants and bars aren’t elaborate enough, it said. “So the area does not conform to the more whole-hearted objective inherent in the mixed-use concept.”

That certainly explains it.

I had an interesting discussion with Marc Hays, senior VP of leasing, specialty centers, for Cleveland-based Developers Diversified Realty. I’ve talked to Marc a number of times, and it was no surprise to me that he was pretty flexible in his definition of mixed-use—a prerequisite in our industry. But he did offer up an expanded idea of the format—that mixed-use doesn’t only have to be a mix of different components (a mixing-and-matching of retail and residential and office, for example, or a dash of the unusual in the form of a racetrack, aquarium or hospital), but could be a melding of different types and scales of retailers within a single center. He cited cases where upscale and discount (just for illustrative purposes, think Neiman Marcus and Big Lots, Nordstrom and T.J. Maxx) would co-exist to provide a true one-stop-shop experience for customers.

Other developers I talked with shared a vision that mixed-use could entail a retail/entertainment center adjacent to a housing component or a school—disparate properties that serve potentially the same user.

Which view is correct? Is mixed-use an aesthetic combination of Main Street retail, with office atop shop? Or is it a sprawling complex that incorporates a mall next to an apartment building next to Class A office space? Or is mixed-use a strategic mix-and-match of diverse retailers?